Michele Surdi

Publisher's note: Occasionally, readers feel compelled to share their findings in more formal ways than our lettersfeedback section. Michele Surdi has done so before. Having confirmed my own previous findings—on the FirstWatt F5 amp of which he acquired a sample—my review of the HPA-1 ending in an award tweaked his own curiosity. Contacting his local Pass importer for a short-term loaner, here are his thoughts. - Ed

It all began with headphones. Hitching a Koss Pro4A (still going strong on Amazon I see) to the family's Collaro record changer through an unspeakable dangling switch box, I discovered that some of my discs had two channels! The tiny voices in the Stones' Like a Rainbow chorusing in my left ear had me hooked for good and ever. Since then I've owned anything from the redoubtable Koss ESP-9 electrostatic skull crusher to the ever-glorious Sennheiser HD 414x (bring 'em back, bring 'em back) but by and large, cans leave me cold. Big cones and big floor spaces spell adult hifi for me. Big cones also spell low power better quality amps. Over time, I've gathered a representative little posse. So when Srajan raved over the Pass HPA-1, the idea of using it on my stalwart Sennheiser PX100 portables left me totally unmoved. Yet its preamp capabilities—he'd really called this a muscle preamp—raised the irresistible Pass siren call once more.

If memory serves, the last solid-state preamp in my life had been a deservedly forgotten Nakamichi 410. On one hand then, the bar set for the HPA's preamp functionality was not unduly high. On the other however, the HPA would be contending with my mint Nagra PL-P. This, Jean Claude Schlup's first creation and Nagra's original entry in the hifi stakes, has been discontinued a few years ago since, as Audio Technology's marketing rep personally told me, the new Nagra brand couldn't make money on it. Be that as it may, the PL-P is a mains-charged battery operated affair powered by eight tubes including the phono stage. That's actually its raison d'être but I've never used it due to my unloving memories of vinyl's snap, crackle and pop. Its chief attraction to me lies in the twin input pots. Those can be used to control the tape output in hotrod mode, bypassing both the main volume control and two pairs of tubes. This results in a presentation I find more suitable to small ensembles while the full broadside version is generally appropriate to higher energy fare. The comparison then—which we will not call a shootout—is with a €10'000+ highly specialized machine (the HPA's price in Italy being less than half, €4'615 to be exact).

Amps employed, as I have stated with some swagger, are representative of various topologies with a putative power delivery ranging from 25 to 2.5 watts: a hybrid push-pull DHT, Schlup's Nagra 300p, Nelson's own celebrated push-pull Mosfet F5, the irreducible Trends TA-2p SE Tripath canned chip and a new entry, a bona fide 2A3 SET custom-made for me by Attilio Caccamo of Tektron. Since all the other amps have been repeatedly covered in these pages, a brief description of the Tektron TK2A3 is obligatory. The way I see it, if you choose a quirky solution like a single-ended DHT setup, the two things you want to have control over are price and production values. Admittedly circuit layout is best left to professionals but a trusted builder is, to my mind, almost indispensable for this kind of stuff. So it was that after conferring with Attilio (see my 6moons notes for his previous confidence building efforts), I opted for the venerable 2A3 with traditional tube rectification and choke.

A budget was laid out and on Attilio's insistence, invested chiefly in premium passive components instead of sexy NOS tubes. Expert readers will recognize Vishay propylene, Philips Teflon and Auricaps with Roederer and smaller Auricaps voicing the drivers. The small tubes are the excellent and by now unobtainable Italian Fivre 6SN7. The regulator is a rugged RCA 5V4G while the big bulbs are the inscrutable Chinese Shuguangs. One of these validated a sinister Orientalist stereotype by developing a venomous hiss after ten hours or so of use. Attilio was informed and over the weekend sent me a new matched pair which has labored diligently ever since. Big-ticket Krons are available as an upgrade while aspirational augmentations in the shape of WBT terminals and inputs were requested and patiently supplied. The end product is wholly satisfactory, particularly in view of its price which, though typically on request, is a very far cry from, say, the €14'250 sticker of my Nagra 300p.